It is known to separate carbon dioxide from other gases by adsorption. For example, U.S. Pat. No. 5,156,657 discusses the removal of water vapor and carbon dioxide from air by PSA and TSA. Similarly, it is known to separate alkenes from alkanes by adsorption. U.S. Pat. No. 4,917,711 describes the adsorption of an alkene from a mixture containing the alkene and an alkane using an adsorbent comprising a copper compound and a high surface area support such as silica gel or zeolite molecular sieves, such as 4A zeolite, 5A zeolite, type X zeolite or type Y zeolite.
U.S. Pat. No. 5,365,011 describes the separation of alkenes having 2 to 6 carbon atoms from alkanes having 2 to 6 carbon atoms by pressure swing adsorption at temperatures in the range of about 50 to about 200.degree. C. using 4A zeolite. The 4A zeolite may have up to 25% of its exchangeable sodium ions replaced by other ions, including potassium ions, calcium ions, strontium ions, etc., provided that the presence of the other ions does not cause the 4A character of the adsorbent to change.
Breck et al, "The Properties of a New Synthetic Zeolite, Type A", Journal of the American Chemical Society, Vol. 78, Number 23, 1956, pp. 5963-5977, describes the adsorption of carbon dioxide and various hydrocarbons using partially potassium-exchanged type 4A zeolite.
Because of the importance of adsorption as a method of separating carbon dioxide from other gases, including hydrocarbons, adsorbents having enhanced carbon dioxide-adsorption properties are continuously sought. This invention discloses the use of a class of type A zeolites for effective separation of carbon dioxide from gaseous hydrocarbons.